Prevention of influenza

Etiotropic therapy: core principles

The modern anti-influenza strategy recommended by the WHO relies on the use of chemical agents that directly block viral replication. The key factor for success is time: medications must be prescribed within the first two days (48 hours) from the onset of the illness, without waiting for the results of laboratory verification.

An early start helps shorten the fever period, reduce the severity of acute respiratory manifestations, and significantly lower the risk of complications. However, even with delayed patient presentation, etiotropic agents remain relevant, especially in severe and complicated cases of the disease.

Antiviral drugs are conventionally divided into agents with proven direct action (viral release inhibitors, endosome escape inhibitors, viral entry inhibitors) and agents with complex effects on the virus and the host immune system (interferons and their inducers).

Neuraminidase inhibitors: Oseltamivir and Zanamivir

This group of drugs selectively inhibits the neuraminidase enzyme, depriving new viral particles of the ability to leave the infected cell. As a result, the spread of infection through the body is halted. The drugs are equally effective against influenza virus types A and B.

Oseltamivir has a systemic effect and is the first-line agent. It is available in capsules and powder for suspensions.

• For adults and children aged 12 and older (or weighing over 40 kg): prescribed at 75 mg orally twice daily for a 5-day course.
• For children aged 1–12: the dose is calculated based on weight (30 mg for weight up to 15 kg, 45 mg for 16–23 kg, 60 mg for 24–40 kg) twice daily.

Use is permitted in pregnant women. In severe influenza, doubling the daily dose is acceptable regardless of the day of illness. Clinically significant resistance to oseltamivir is extremely rare and is typically not transmitted from person to person.

Zanamivir is used exclusively via oral inhalation (5 mg per dose) and is approved only for children over 5 years of age.

M2 channel blockers: Rimantadine

Rimantadine acts at the stage of viral escape from the endosome by blocking ion channels (M2 protein). Its significant drawback is a narrow spectrum of activity: it is effective only against influenza type A (suppresses the H1N1 strain) and does not inhibit the replication of H3N2, H5N1, and pandemic pH1N1 strains at all. Furthermore, the drug has no positive effect if the patient has already developed pulmonary complications.

Regimens for adults:

1. Gentle regimen: 100 mg twice daily for 5 days (for elderly individuals, the daily dose is reduced to 100 mg).
2. Loading dose regimen: 300 mg on the first day, reduced to 200 mg on the second, to 100 mg on the third, followed by 200 mg thereafter.

For children, a 0.2% solution (syrup) is used. Toddlers aged 1–3 are given 0.5 mg/kg (gradually decreasing the frequency from three times to once daily); dosages are increased for older children. When prescribing, one must keep in mind adverse effects: gastrointestinal (nausea, dyspepsia) and neurological (insomnia, anxiety, depression).

Antibacterial and pathogenetic therapy

If a bacterial flora joins the viral infection with the development of pneumonia, the administration of antibiotics active against gram-positive microorganisms, penicillin-resistant staphylococci, and H. influenzae is indicated.

• Oxacillin, Cefuroxime, Ciprofloxacin, Vancomycin, Clindamycin, Imipenem, or Amoxicillin/clavulanate are used as baseline therapy.
• In severe pneumonia, treatment is switched to combination regimens: third-generation cephalosporins (Ceftriaxone, Cefotaxime) along with macrolides (Azithromycin, Clarithromycin). Respiratory fluoroquinolones (Levofloxacin, Moxifloxacin) serve as an alternative.

As part of the pathogenetic therapy for severe respiratory distress syndrome, Surfactant-BL inhalations (100 mg/kg every 6–10 hours) are actively used. This complex of phospholipids and proteins reduces surface tension in the pulmonary alveoli, preventing their collapse, restores the epithelium, enhances macrophage activity, and helps remove toxins along with sputum. Intravenous administration of high doses of acetylcysteine and the use of mucolytics also yield positive results.

Briefly: answers to topical questions

What else to study on this topic

• Mechanism of action of interferon series drugs and interferon inducers.
• Viral entry inhibitors (umifenovir).
• Clinical features of viral-bacterial pneumonia.
• Complete administration regimens for respiratory fluoroquinolones and their side effects.

Other topics in the "Respiratory Infections" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.